Asymmetric transfer mode (ATM) virtual circuit (VC) bundle management allows configuration of multiple VCs between any pair of ATM-connected network devices such as routers. Conventionally, such a bundle management is limited to permanent virtual circuits (PVCs). Each of the multiple VCs has its own quality of service (QoS) characteristics, ATM traffic class, and ATM traffic parameters, but are grouped into a bundle and coupled to the same destination. These PVCs referred to as bundle members. Using PVC bundles, differentiated service can be provided by flexibly distributing IP precedence levels over the different PVC bundle members. A single precedence level or a range of levels can be mapped to each discrete PVC in the bundle, and individual PVCs in the bundle carry packets marked with corresponding precedence levels.
FIG. 1 schematically illustrates a conventional ATM PVC bundle implementation. A source network device 10 (such as a router) typically receives data IP packets carrying different IP precedence levels from various networks (or other routers) and host computers. A bundle 12 of PVCs is coupled from the source network device 10 to a destination network device 14 through an ATM network 16. Each path of PVCs has to be explicitly configured throughout the network. That is, all of the links between the endpoints are manually configured for each of the member PVCs in accordance with IP precedent levels. The IP precedent level is carried, for example, by the value set in the IP precedence bits of the type of service (ToS) byte of the header of a packet.
Switched virtual circuit (SVC) bundles have also been implemented in order to alleviate the PVC bundles' configuration intensive feature, in which the user (system administrator) manually configures the source and destination endpoints, and the paths between the endpoints are set up automatically. However, manually configuring each of the member SVCs (currently up to 8 member SVCs) at both endpoints is still cumbersome, and also susceptible to configuration errors and mismatches.
There is the third of VCs: Soft Permanent Virtual Circuits (SPVCs). An SPVC is a hybrid of the PVC and SVC, and typically includes PVC connections at the both end and an SVC connection therebetween. For example, a first PVC is set up from an edge router to a first network device, an SVC is set up from the first network device to a second network device via a communications network such as ATM network, and a second PVC is set up from the second network device to an edge router. Typically, the SVC connection is set up inside a “trusted” network such as a Service Provider network or a private corporation network, and the edge routers are outside of the secured or private network and thus “un-trusted.” An SPVC can be explicitly configured using the PVC portion. The SVC portion of an SPVC can be automatically rerouted in case of a link-failure or the like, implementing clear retry mechanism. SPVCs are important and widely-deployed connection type in ATM network implementing scalable and dynamic routing protocols such as Private Network-Node Interface (PNNI).
However, although SPVC connections are preferred by many users and widely used in various scenarios, there is no VC bundle management for SPVCs coupling across a communications network such as an ATM network. That is, even if an incoming connection (IP packets) may carry IP precedence levels, for example, in the ToS byte of the IP header, there is no mapping of IP precedence levels to SPVCs. Thus, all of IP packets with various IP precedence levels are carried to the destination by a single SPVC with a given characteristic. This results in the loss of QoS preservation across the ATM network when SPVCs are used to carry IP traffic.